Current U.S. Government regulations require vehicle headlamps that permit the use of replaceable bulbs to have bulb retainers capable of accepting and retaining such bulbs. In order to comply with these regulations, it is also common for vehicle manufacturers to use a bulb shield to reduce the light emitted from these bulbs so as to reduce headlamp glare (uncontrolled light) to thereby meet U.S. Government specifications regarding light output from the headlamp assembly. Examples of headlamp assemblies using the above arrangements may be found by a review of Liverance et al U.S. Pat Nos. 4,926,301 and 4,882,606, commonly assigned.
In some cases, it is preferred to preassemble the bulb retainer and bulb shield together, and at a later time assemble this subassembly to the headlamp reflector by inserting the shield from the rear of the reflector, through an opening (or central bore) of the reflector. This concept of preassembling the shield to the retainer for later assembly through the central bore in the housing from the rear of the reflector has implications on vehicle headlamp design and performance. One area affected is that of the central bore. With this concept, the size of the central bore restricts the size of the bulb shield to a size smaller than the central bore of the reflector housing. Regarding the central bore size, if it is too large in size, this can create problems, some of which are bulb positioning (loss of light output from bulb mispositioning), loss of reflector surface (loss of light output), opportunities for dirt entry, and other factors. If the central bore is too small, there can be a restriction in bulb shield size. Restriction of the bulb shield size can adversely affect a number of vehicle headlamp areas including shield tolerances and effectiveness, temperature buildup around the bulb, bulb life, mounting of ornamental or decorative caps to the shield, light output, headlamp quality rating, and other factors. Also, in most headlamp assemblies which use a shield and a bulb retaining device, the shield and/or bulb retainer must be affixed to the headlamp reflector with one or more fasteners.